This invention relates to coil-type dialyzers or membrane diffusion devices of the type used in artificial kidney systems; and more particularly, to a membrane support member for use in such devices.
Coil dialyzers used in artificial kidneys, such as the one disclosed in U.S. Pat. No. 3,743,098, include an elongated, tubularly-shaped semipermeable membrane and a membrane support member which are wound together about a cylindrical core. Blood from a patient flows through the dialyzer inside the membrane and dialysis solution flows through the dialyzer in a crosswise direction. The dialysis solution flows between the windings of the membrane and support member so as to contact the membrane and receive bodily waste products from the blood.
The membrane support disclosed in U.S. Pat. No. 3,743,098 is a foraminous screen. Recently, less expensive embossed support members have been developed which include an imperforate center web having equal-height support ribs on each side. The ribs engage and position the membrane in the dialyzer, as well as define flow channels between the support member and membrane for the dialysis solution.
The membrane is made of cellophane or cellulose derivative, such as is sold under the trade name Cuprophan. Such materials have the characteristic of stretching more in the transverse direction than in the longitudinal direction. It is believed that when the embossed support members are used, the transverse stretching of the membrane may permit the sides and longitudinal edges of the membrane to contact the web, and thereby reduce the effectiveness of the dialyzer by inhibiting flow of the dialysis solution.
It is therefore an object of this invention to provide an improved embossed support member which prevents the sides and longitudinal edges of the membrane from contacting the support member web.
The foregoing and other objects and advantages will be apparent from the following description and appended claims taken in conjunction with the accompanying drawings.